Plastic composition



Patented Feb. 22, 1949 PLASTIC COMPOSITION Andrew C. Buechele, Minneapolis, Minn., as'signor to General Mills, Inc., a corporation of Delaware ' No Drawing. Application January 5, 1946,

Serial No. 639,422

Claims.

The present invention relates to a plastic composition which is particularly adapted for use in the production of radio loop antenna.

Many radio receivers are equipped with fla spiral loop antenna within the cabinet. It is important that these antenna have constant and substantially permanent electrical characteristics. This implies constant dimensions of the antenna. However, these antenna are subjected to Wide temperature variations, making it difi'icult to maintain the dimensions of the antenna constant. For example, the temperature within many radio cabinets reaches 190 F.; thus an antenna may be subjected to variations of from about room temperature, or 70 F., to 190 F.

One type of construction of these loop antenna which is currently in use involves a slot cut spirally in a rigid flat insulating board which serves to hold the loop of wire in the desired pattern where it may be sealed by an adhesive agent, wax, or similar means. This type of construction imposes limitations on speed of production as well as on the closeness of adjacent layers or loops of winding. Furthermore, it requires a fairly heavy thickness of insulating board which must be of relatively strong and tough character.

Heretofore it has not been practical to eliminate the slot and to relay solely on an adhesive for retaining the loops in a desired configuration. Adhesive and binding materials heretofore available did not possess the desired characteristics of tackiness and freedom from brittleness over a sufiiciently wide range of temperature, to permit the construction of an antenna without the employment of the customary slot.

The present invention involves a composition which permits the construction of loop antenna without the employment of the customary slot. It involves a plastic composition possessing ample adhesive properties under the conditions of preparation and use, as well as the desired electrical properties such that it is possible to prepare an antenna which will stand wide fluctuations in temperature and appreciable mechanicalshock without undue effect on the electrical characteristics of the antenna.

It is, therefore, an object of the present invention to provide a plastic composition possessing plasticity and adhesiveness over wide temperature ranges and possessing adequate electrical insulation characteristics. It is a further object of the present invention to provide a plastic composition particularly adapted as an adhesive for the production of radio loop antenna, said composition possessing toughness, strength, dimensional stability, tenacity, and strong adhesion under conditions of use, as well as the proper degree of initial fusibility.

These and other advantages of the invention will be more fully apparent from the following description with particular reference to the specific examples which are to be considered as illustrative only.

The novel plastic composition is composed of a major proportion of a polyamide resin of the type commonly knownas Norelac which type of resin is the polyamide reaction product of a polyfunctional amine and a polyfunctional acid derived from the polymerization of fatty acids. In addition the plastic composition contains a minor proportion of a polymerized rosin. The Norelac type of polyamide is described in "Oil and Soap, 21, 101-107, 1944. Preferably, it jis prepared by the reaction of ethylene diamine with dimeric and higher polymeric acids or esters derived from vegetable oils. Considerable variation, however, is permitted in the type of polyfunctional amine and in the polyfunctional acid. Such polyfunctional amines as hydrozine and 1,6- hexanediamine and numerous others may be used in place of the ethylene diamine. The polyfunctional acids contemplated by the present invention include all of the dimeric and higher polymeric acids derived from higher fatty acids. A typical polyamide employed in the present invention may possess the following characteristics: softening point 105-115 C., ASTM ring and ball method; penetration 4-12, ASTM D5-25 with 200 g. weight for 30 seconds at 25 C.; a Gardner- Holdt viscosity of AD as 35% solids in equal parts of toluene and n-butanol; gel time in excess of 10 seconds in a thin film on a hot steel plate at a temperatureof- 200 0., when intended for a solvent application, or in excess of 500 seconds when intended for hot melt application. In addition to these properties, some of the polyamides have atendency to age towardinsolubility and infusibility without loss of other advantageous properties, thus rendering antenna made therewith more permanent.

,iezrs I Considerable variation is also possible in the polymerized'rosin employed. This constituent, however, is preferably a polymerized rosin of the type marketed by Hercules Powder Company under the name Poly-pale" which is derived from rosin acids by an acid catalyzed polymerization through their double bonds to a product containing approximately polymers and normal rosin constituents. Such a product may possess a softening point of about 93 C. (ASTM ball and ring) acid number 150 and saponiflcation number 163. Other polymerized rosins possessing the same general characteristics may also be used. v

The composition may be prepared by simply admixing the constituents and heating to a point at which a homogeneous mixture results. Where the composition is intended for hot melt application the use of solvents is preferably avoided in the preparation of the mixture. Where, however, the mixture is desired in the form of a sprayable liquid, suitable solvents such as xylol and n-butanol may be employed. A board suitable for the production of antenna may be prepared by coating with the plastic composition either by hot melt application or by means of the liquid solution, in accordance with well-known procedures.

The antenna may be prepared by laying a heated wire on the board coated with the plastic composition at a rate allowing local fusion of the film and retention of the wire by the film to produce the antenna loop pattern. Alternatively, the wire may be preformed into a loop and may board containing the film of the plastic composition. As a further alternative, the preformed loop, in an unheated condition, may be placed on the board containing the plastic composition in a molten condition.

Example 1 A sprayable liquid was made with non-volatile, material containing nine parts by weight of polyamide ED-94, a product of the reaction of ethylene diamine with dimeric and higher polymeric acids or esters derived from vegetable oils (softening point 105 C. ASTM ring and ball) and one part by weight of Poly-pale 851 (softening point 93 C.). The volatile solvent in this liquid. was equal weights of xylol and n-butanol. The liquid was prepared by heating equal weights of volatile and non-volatile fractions with reflux and agitation. It was sprayed on a fiat section of insulating board where it dried to a thin film. A heated wire was fed to this film at a rate allowing local fusion of the film and retention by it of the wire in the antenna loo pattern. Alternatively, the wire was placed as a preformed heated loop in the sealing film, which held it on cooling.

After cooling, the wire was found to be retained firmly by the film and thus bound to the insulating board in a mechanically strong unit effectively stable against change of dimensions and of proper electrical characteristics for use conditions.

Example 2 A homogeneous hot melt was made at 130 C. from eight parts by weight of polyamide ED-94, prepared by reaction of ethylenediainine with dimeric and higher polymeric acids or esters derived from vegetable oils, and two parts by weight of "Poly-pale 351, a polymerized rosin then be heated and applied to the of ring and ball softening point 93 C. This hot melt was found to give a product of requisite physical properties for use as a film for mounting a loop antenna as described in Example 1.

Example 3 A homogeneous hot melt was made at 130 C. from nineteen parts by weight of polyamide ED-94, a product of reaction of ethylenediamine with dimeric and higher polymeric acids or esters derived from vegetable oils, and one part by weight of Poly-pale 851, a polymerized rosin of ring and ball softening point 93 C. This hot melt was found to give a product of the requisite physical properties for use as a film for mounting a loop antenna as described in Example 1.

Example 4 A sprayable liquid was made by heating together the following materials with reflux and agitation: 60% by weight non-volatile composed of 9 parts by weight polyamide ED-94 prepared by reaction of ethylenediamine with dirneric and higher polymeric acids or esters derived from vegetable oils, and 1 part by weight Poly-pale 851," an .acid polymerized rosin of ring and ball softening point 93 C.; and 40% by weight volatile composed of 1 part by weight phenol and 3 parts by weight xylol. The film resulting from drying a coating applied from this liquid was found to have the requisite physical properties for mounting a loop antenna as described in Example 1.

Some modification of the physical properties in the qualities of the plastic composition such as the hardness, softening temperature, and tack when softened may be effected by variation in the relative proportion in the ingredients. The minor ingredient, namely the polymerized rosin may be varied from a small percentage, 24%. up to about 20%, without seriously affecting its properties for this particular purpose.

Variations both in the composition, in the method of preparing the board, and in the method of producing the antenna may be made without departing from the spirit of the invention. Moreover, it will be apparent that the present composition, while particularly adapted for the production of loop antenna is also feasible for numerous other uses. It is to be understood, therefore, that the invention is to be limited only by the following claims.

I claim as my invention:

1'. A plastic composition comprising a major proportion of a polyamide of a polyfunctional amine and a polyfunctional acid derivable from the polymerization of higher fatty acids and their esters, and about 2 to 20% of a polymerized rosin.

2. A plastic composition comprising a major proportion of a polyamide of a polyfunctional aliphatic amine and a polyfunctional acid derivable from the polymerization of higher fatty acids and their esters, and about 2 to 0% of a polymerized rosin.

3. A plastic composition comprising a major proportion of a polyamide of a polyfunctional amine and a polyfunctional acid derivable from the polymerization of linoleic and linolenic acids and their esters, and about 2 to 20% of a polymerized rosin.

4. A plastic composition comprising a major proportion of a polyamide of ethylene diamine and a polyfunctional acid derivable from the polymerization of linoleic and linolenic acids and 23111 esters, and about 2 to 20% of a polymerized REFERENCES CITED 5. A plastic composition comprising a major The following references are of record in the proportion of a polyamide of a polyfunctional file of this patent: amine and a, polyfunctional acid derival le from 5 UNITED STATES PATENTS the polymerization of higher fatty acids and their esters and about 2 to 20% of a polymerized Number Name Date rosin containing approximately 40% polymer- 2,379,413 Bradley July 3, 1945 ized rosin acids and approximately 60% unpoly- OTHER REFERENCES merized rosin acids. 10

Paint Manufacture XIII, July 1943, pages 161 ANDREW C. BUECHELE. and

Oil and Soap. 21. April 1944, pages 101407 

